How do you figure cerebral damage? The cerebral cortex is located near the stem of your brain in the sub cortex area. Unless he swung at the back of the head and hit the right spot your actually most likely looking at damage to the parietal lobe/ frontal lobe.

Oh, we're giving real advice here? My bad, let me start over: Get better friends or expect frequent trips to the hospital, because everything else is not worth the effort. Edit: Had to edit this really fast to make fun of the fact that you genuinely suggested you let childish people stay childish.